Conventional and elementary sliding rotary vane machines are distinguished from virtually all other fluid displacement machines in their remarkable simplicity. On the other hand, such machines exhibit relatively poor operating efficiency. This poor energy efficiency is rooted directly in machine friction, both mechanical and gas dynamic. As is well known, the predominant source of mechanical friction in conventional production non-guided vane rotary machines occurs at the intense rubbing inter-face of the tip of the sliding vane and inner contour of the stator wall. Furthermore, governing the motion of the vane by the stator wall contour necessarily and greatly inhibits the area through which gas can enter or exit the machine. This results in increased fluid flow pressure losses in the inlet and outlet port regions of such type machines.
Over the years, many means have been proposed to eliminate guiding the radial motion of the vanes through the direct action of the vane tips rubbing along the inside casing or stator wall. In a majority of previous endeavors to grapple with this mechanical problem, attention has been focused upon the use of wheels or rollers pinned to the sides of the vanes wherein these rollers follow inside a circular or non-circular track of the appropriate configuration. The cooperation of the rollers in the roller guide track then produces a means of dictating the radial location of the vane which is pinned to the roller follower and hence determines the position of the tip of the vane.
As attractive as this approach first appears to be, roller wheels contain an overwhelming flaw: They cannot provide positive bi-axial radial motion without having to reverse their rotational direction. That is, vanes constrained by rollers can accommodate geometric displacement in only an outward or inward direction at any one time.
As an example, if the roller has been in contact with one side of the track, and because of this, it has been turning in the clockwise direction, and then should the roller be caused to come in operative contact with the other side of the guide, the roller will be turning in what may be regarded as the wrong direction. As a consequence, each roller undergoes skidding inside the track until they are stopped. Then each vane roller must reverse rotational direction and accelerate to the speed which will match the motion dictated by the other side of the roller guide. Because, in practice, vane machines generally require both positive inward and outward vane motion, rollers become impractical or non-functional in real machines where both motions are often demanded.
Other innovators have taught the use of sliding arc segment tethers in place of vane rollers. In such prior art instances, the arc segment tethers are captured within a circular annular groove that may or may not be rotatable. The arc segment vane tether has the outstanding and fundamentally important advantage of being able to deliver both positive inward and outward radial motion to the vane simultaneously. However, in the prior art, vane motion control techniques used arc segment vane tethers which entailed considerable mechanical friction that arises from the sliding of the arc tether surfaces against the circular annular guides, whether or not the guides themselves are rotatable.
Further, and of fundamental importance, previous workers have failed to provide teachings of the specific contour that the internal casing profile must take on in order for the vane tips to mate closely in a non-contact but sealing relationship with this casing contour profile. Earlier innovators have either simply erred and believed that the proper casing contour was "circular", or circumvented the fundamental issue by characterizing the shape of the internal casing contour with words such as "substantially circular" and not teach operatively just how this shape is determined.
As will be seen in considerable detail hereinafter, the present invention not only eliminates the majority of the mechanical sliding friction endemic to previous techniques, but it does so with fewer and simpler components than were required by the prior art. At the same time, this invention accomplishes the fundamentally important positive bi-axial radial vane motion control necessary for the practical operation of such machines. Finally, my invention accommodates the natural motion of the tips of circularly-tethered vanes by providing exceedingly close non-contact vane tip sealing as a result of properly shaping the mating or conjugate interior of the casing wall.